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Informist, Wednesday, Jan. 21, 2026

MUMBAI – While the La Nina event persists over the tropical Pacific Ocean, the recent warming of the sub-surface temperatures may indicate early stages of La Nina's decline, the Australian Bureau of Meteorology said in its fortnightly report. The bureau's model, consistent with other international models, indicates a return to neutral El Nino-Southern Oscillation conditions in late summer, and some of these models predict a further transition into El Nino from June.

Summer in the Southern Hemisphere spans from December to March.

The El Nino-Southern Oscillation index value for the week ended Sunday was (-)0.91 degrees Celsius, consistent with La Nina patterns, the bureau said. Though atmospheric indicators such as trade winds, pressure, and cloud patterns in the central tropical Pacific continue to show consistent signs of La Nina, they have grown relatively weak, the bureau said. 

Ocean surface temperatures in the tropical Pacific between (-)0.80 degrees Celsius and 0.80 degrees Celsius are considered to be neutral conditions, while sustained values below (-)0.8 degrees Celsius for at least three months are considered indicative of a La Nina event.

As of Sunday, the 60-day and 30-day Southern Oscillation Index values were 5.9 and 8.8, close to La Nina thresholds, which require the values to be greater than 7. Forecasts of the Madden-Julian Oscillation suggest that trade winds may weaken in the coming fortnight, which could contribute to the breakdown of the La Nina pattern, it said.

The Southern Oscillation Index tracks the atmospheric part of the El Nino–Southern Oscillation, while the Oceanic Nino Index tracks the ocean part. The Southern Oscillation Index compares the difference from average air pressure in the western Pacific, measured in Darwin, Australia, to the difference from average pressure in the central Pacific, measured in Tahiti.

Post transition from La Nina, neutral El Nino-Southern Oscillation conditions are likely to persist at least till late autumn. Autumn in the Southern Hemisphere is from March to May. While some international weather and climate models assessed by the bureau suggest the possible development of El Nino from June, predictability of such models beyond autumn is generally low during this time of the year, the bureau said.

The El Nino-Southern Oscillation refers to the fluctuation between El Nino and La Nina conditions in the Pacific Ocean. El Nino is linked to drier and hotter weather in India while La Nina results in more favourable rainfall. 

The Indian Ocean Dipole is expected to remain neutral at least till the end of autumn, the bureau said. The Indian Ocean Dipole is the difference in surface temperatures between the eastern and western tropical Indian Ocean. A negative Indian Ocean Dipole leads to less rainfall in India, while a positive index leads to more rainfall and a neutral phase signals no significant change in precipitation. For monitoring the index, the bureau considers sustained values above 0.4 degrees Celsius for at least eight weeks as typical of a positive index and values below (−)0.4 degrees Celsius for the same duration as typical of a negative index.

For Jan-Mar, the India Meteorological Department has forecast below normal rainfall across the country at 88% of the long-period average. The prevailing La Nina conditions are expected to persist for another month or two before transitioning to El Nino-Southern Oscillation neutral conditions during Jan-Mar, the Indian weather department said.  End

Reported by Shreya Shetty

Edited by Avishek Dutta

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